[Python-Dev] PEP czar for PEP 3144? (original) (raw)

Terry Reedy tjreedy at udel.edu
Mon Mar 19 23:44:44 CET 2012

On 3/19/2012 6:04 PM, Guido van Rossum wrote:

On Mon, Mar 19, 2012 at 2:58 PM, Peter Moody<pmoody at google.com> wrote:

On Mon, Mar 19, 2012 at 12:55 PM, Guido van Rossum<guido at python.org> wrote:

On Mon, Mar 19, 2012 at 12:37 PM, Ethan Furman<ethan at stoneleaf.us> wrote:

Nick Coghlan wrote:

Collapsing the address list has to build the result list anyway to actually handle the deduplication part of its job, so returning a concrete list makes sense in that case.

Having only one function return a list instead of an iterator seems questionable. Depending on the code it could either keep track of what it has returned so far in a set and avoid duplication that way; or, just return an iter(listobject) instead of listobject. I know I'm lacking context, but is the list ever expected to be huge? If not, what's wrong with always returning a list? It's possible to return massive lists, (eg, returning the 4+ billion /128 subnets in /96 or something even larger, but I don't think that's very common). I've generally tried to avoid confusion by having 'iter' in the iterating methods, but if more of the methods return iterators, maybe I need to rethink that? I personally like having 'iter' in the name (e.g. iterkeys() -- note that we dropped this in Py3k because it's no longer an iterator, it's a dict view now. But I don't want to promote that style for ipaddr.py.

I am not sure which way you are pointing, but the general default in 3.x is to return iterators: range, zip, enumerate, map, filter, reversed, open (file objects), as well at the dict methods. I am quite happy to be rid of the 'iter' prefix on the latter. This is aside from itertools. The main exceptions I can think of are str.split and sorted. For sorted, a list must be constructed anyway, so might as well return it. This apparently matches the case under consideration. If name differentiation is wanted, call it xxxlist.

-- Terry Jan Reedy

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